The present innovation relates to a machining unit for machine tools with several machining stations As is known from the prior art, for the automatic machining of components, such as for example valves, water cocks and similar parts, the chip removing machining is carried out in consecutive operations by a large number of machining stations, for example by turning, drilling, thread cutting or similar machining In this connection the workpieces are arranged on a rotating faceplate in the machine tool The tools of the machining units used carry out the necessary feed movements using NC motors In the known machining units of this type, an axial arrangement of the spindle mounting and of a threaded spindle for feeding the spindle mounting is provided, the threaded spindle being mounted in a stationary stop nut on the rear side of the spindle mounting
This known construction has the disadvantage that the machining unit has a considerable length and thus a considerable space requirement. It has already been attempted to reverse the arrangement between spindle mounting and driving spindle for the tool feed. In this case the driving spindle projects from the housing on the tool side, that is to say in precisely the place in which the machining of the workpiece is carried out, as a result of which the threaded spindle is exposed to constant dirtying which is caused by chip deposits and coolant deposit. This can lead to impairment of the free rotation movement of the threaded spindle in the threaded nut. It has also been attempted in embodiments of this type to eliminate the dirtying problem of the freely protecting part of the threaded spindle in the vicinity of the tool by providing concertina guards. In addition to a considerable spaced requirement for these guards, such an embodiment has the disadvantage that there is a certain inertia when the displacement movement of the threaded spindle is carried out. This inertia arises as a result of the frictional forces which exist and as a result of the fact that in the known embodiments the rotation movement of the threaded spindle takes place with the interposition of bearings which, although they permit a rotation movement of the threaded spindle, impede a displacement of the same in an axial direction. Furthermore, in known embodiments, the threaded spindle is arranged rigidly on the sleeve-shaped component or incorporated directly in the sleeve. As, in these known embodiments of the sleeve-shaped component, both the tool spindle and the bearing of the spindle are to be accommodated in the sleeve-shaped component, it was necessary to provide threaded spindles with large dimensions, and thus the threaded nut also had to have large dimensions with the result that the device has considerable inertia.
In the known embodiments, which have considerable extension in the axial direction and bearing points in only two places which are relatively far from one another, eccentric forces can act upon the tool during machining of the workpiece, forces which lead to a transverse loading of the mounting device of the tool spindle and thus cause a deviation of the axis of the workpiece. In the known embodiments, the threaded spindle/threaded nut axis is displaced axially in relation to the axis of the mounting sleeve and the tool spindle. This particular arrangement frequently leads to overstressing of the bearings of the sleeve, as a result of which stresses with a component perpendicular to the feed axis arise, which has a negative influence on the working accuracy and the service life of the machine components. The known machining units are thus not in a position to meet the demands placed on machines today.